Please help me go in the right direction with my 93 ls400 w/140k miles.

When the car is in park the idle fluctuates from 550-700.

When the car is in drive the idle becomes more erratic and fluctuates from 700-300.

When car is driving on the road I can feel the idles drop for a split second then recovers.

My question is I received a $75 coupon from Lexus. I think my ignition timing may be the cause or the idle air control valve or throttle position sensor or my timing belt is worn (it has cracks)

Should I tell them to diagnose the idle problem or go ahead and have them check the timing and adjust if necessary. I only have enough money to do one or the other.

I think the timing may be off because of the condition of the car was bad when I bought it. I changed the air filter, cleaned the throttle body, seafoamed the intake, changed the fuel filter et cetera.

any suggestions would be appreciated.

 

use the money to buy the parts and DIY

 

Is it throwing any codes?

Have you done a tune-up?
plugs, wires, caps, rotors, fuel filter...

 

i just did the same on my 93 lexus ls400 137,000
the timing is not so hard
if your considering doing it yourself what ever you do do not mess with any other components like spark plugs especially not the throtle body and injectors like that if something does go wrong you dont have to put any other variables in
ooohhh and buy gates parts if DIY i bought ebay stuff its crap
still ended up buying gates
duralast is the same thing as ebay

 

there is a neat trick to find codes if you dont have the scanner its on the lexus tutorials

 

no codes.

I wish there were so I could know what is going on. ALso, after i seafoam'd the intake the problem went away for one drive. after that it gradually came back.

 

no codes, i have done plugs, wires, and fuel filter. I was going to have the caps and rotor replaced at the same time as the timing belt in january

 

that doesnt apply to 95+ cars as they're all built to OBDII specs.
hunt for a vacuum leak....and make sure your ECU isnt in the part number range for those that were recalled.

 

The $75 coupon you have, is it like cash or do you have to spend to save? The timing can't be adjusted. If there is no way for you to figure out the problem without throwing part after part at it, do to finances, have them diagnose it for you. And then, if it can wait, fix it when you do the timing belt in January when you can afford it. That's what I'd do b/c I know how money can be tight.

 

the coupon is just like cash. I can use it towards any service except oil changes. I changed a couple of the vacuum lines without any difference. I'll just go ahead and take it to lexus for diagnosis. In August, I paid lexus $2000 for a rebuilt ecu, state insp and brake hoses, and o2 sensor. Didn't think I would have further issues like this...

I have a new fuel pump and used tps hopefully it is linked to these issues so I do not have to put out more money

 

Let us know how it turns out.
My 1994 Lexus behaves the same way, but only when I'm using the air con.
Since this is my first car, I do not have any references, so I'll have to believe my mechanic when he tells me that that is the expected behavior when using the air con. I'm skeptical though ;-)

BJL

 

neostar43

What area of VA are you in? I live in NoVa and have been curious to hear how Pohankas service department is.

 

i live in va beach, va. i may just swap the used tps with the one on the car to see if I get any different reactions.

I don't understand why seafoam would cure the problem for one drive then it gradually came back.

also, when I first start the car and is in high idle the rpms do not jump around. just after it starts to warm up does it occur

 

i've been doing some more research. it is funny the things you overlook until someone points it out.

A couple of nights ago, I tried to push the car. the rev did not go past 4000 rpms.

after reading an old post, I am going to clean the maf. This maf is actually a replacement for the one that was originally in the car when i bought it.

The erratic rpms was there a couple weeks after I bought the car but went away after i cleaned the tb and replaced the maf and installed a k&n filter. after awhile the problem became worse that is when i noticed that my power steering resevoir was empty. refilled it and problems went away mostly. but then the problems came back. my power steering resevoir has not needed a refill. i disconnected the acv from the ps pump from the intake. that has made no difference. so I will reconnect the lines and clean the maf and see what happens.

is there a particular cleaning solution that is used for the maf that is safe for lexus?

 

I have a 1993 that just hit 280000kms. It does the exact same thing once and a while. I also put in a K&N drop in filter. Make sure not to over OIL the filter as it does get stuck in the MAF. Doesn't hurt to clean it out but be gentle.

As for the power steering if it continues to use fluid then it's the IDLE AIR CONTROL VALUE . You can figure this out when your driving around 60mph or so the steering should be more stiff where as on low speeds should be loose. This is a common problem with 1st gen LS

https://www.clublexus.com/forums/ls4...ing-bible.html

IF you tried changing the IDLE AIR CONTROL VALUE and still doesn't work there is TPS (throttle position sensor)

I had to replace both and the idle is totally normal unless the A/C is on. That's my advice.